Anthrarufin dye and process of making same.



TINTTETD STATES PATENT OFFICE.

ROBERT E. SCHMIDT, OF ELBERFELD, GERMANY, ASSIGNOR TO THE FAR- BENFABRIKEN OF ELBERFELD COMPANY, OF NEWV YORK.

ANTHRARUFIN DYE AND PROCESS OF MAKING SAME;

SPECIFIGATIONfoiming part of Letters Patent No. 65,514, dated September 25, 1900.

Applicat o fi d August 3, 1899. b'erial No, 725 981- (Specimens.)

To 60% whom it may concern.-

Be it known that I, ROBERT E. SoHMIDT, doctorof philosophy, chemist, (assignorto the FARBENFABRIKEN OF ELBERFELD COMPANY,

of New York,)residingat Elberfeld,Germany, have invented a new and useful Improvement in An thraru fin Dyes; and I hereby declare the following to be a clear and exact description of xnyinvention.

In the specification to Letters Patent No. 595,349 I have described the manufacture of a disulfonic acid of paradiamidoanthrarufin, having the formula NH (1) on s OH (at) 61411202 NH, (5) 4 SO H SO H.

I have now found that a valuable new dyestuff can be obtained by subjecting the said disulfonic acid to the action of formic aldehyde in the presence of alkaline bisulfites. In carrying out my new process practically I can proceed as follows (the parts being by weight:) A mixture prepared from one hundred parts of a watery paste of diamidoanthrarufin disulfonic acid, (containing twenty per cent. of this acid,) fifteen parts of a forty-x per cent. formic-aldehydesolution,and,twenty parts of a forty-per-cent. sodium-bisulfite solution is stirred for a short while at about 50 the diamidoanthrarufin disulfonic acid dissolves in water with a pure blue color and is precipitated from this solution by the addition of strong hydrochloric acid, (the color of the solution being at the same time changed into violet,) the water solution of the new dyestufi exhibits no considerable change when subjected to the same condition.

The shades obtained on unmordanted wool in acid baths by means of the new dyestuff are very bright and more greenish blue than those producible with the aid of diainidoanthrarufin disulfouic acid.

When heated with a fifteen per-cent. hydrochloric acid, the new dyestuff is split, di-

- amidoanthrarufin disulfonic acid being separated. By concentrated sulfuric acid the new coloring-matter is dissolved with a yellow color, which is changed into greenish blue on the addition of boric acid. The absorption spectrum of this greenish blue solution is identical with that of the boric ethers of the diamidoanthrarufin disulfonic acid.

Having now described my invention and in what manner the same is to be performed, what I claim as new, and desire to secure by Letters Patent, is

1. The process for producing a new anthrarufin dyestuff which process consists in first heating a mixture prepared from diamidoan- ,t'hrarufin disulfonic acid, a formic-aldehyde r 'solution and a solution of an alkaline bisulfite secondly separating the new dyestuff from the solution thusobtained and finally isolating the same, substantially as hereinbefore described.

2. The herein described new anthrarufin dyestuff being when dry and pulverized a dark-blue powder easily soluble in water with agreenish-lolue color which is not considerably changed on the addition of hydrochloric acid, being split under regeneration of diamidoanthrarutin disulfonic acid when heated with a fifteen-per-cent. hydrochloric acid,dyein g unmordanted wool bright greenish-blue shades, substantially as hereinbefore described.

In testimony whereof I have signed my name in the presence of two subscribing wit- 5 nesses.

ROBERT E. SCHMIDT. Witnesses:

R. E. J AHN, OTTo Konlc. 

